Variable capacity compressors employ a mechanism for adjusting a stroke amount of a piston by changing an angle of inclination of a swash plate by adjusting a pressure in a control pressure chamber, thereby varying a discharge capacity. Known examples of such a compressor include a compressor in which the discharge chamber and the control pressure chamber communicate with each other via the supply passage and the control pressure chamber and the inlet chamber communicate with each other via the bleed passage, and the pressure in the control pressure chamber is controlled by adjusting an amount of refrigerant flowing into the control pressure chamber by adjusting an opening degree of the supply passage by a control valve provided on the supply passage.
In this configuration, when the supply passage is closed by the control valve, introduction of a high-pressure gas from the discharge chamber into the control pressure chamber is eliminated, and the pressure in the control pressure chamber is lowered to substantially the same value as the pressure in the inlet chamber as the control pressure chamber and the inlet chamber constantly communicate with each other via the bleed passage, and thus the compressor is operated at the maximum capacity. When the supply passage is opened by the control valve, the high-pressure gas is introduced from the discharge chamber to the control pressure chamber, and a refrigerant gas flows out from the control pressure chamber to the inlet chamber via the bleed passage. However, as the pressure in the control pressure chamber increases, the discharge capacity of the compressor is controlled by adjustment of the opening degree of the supply passage by the control valve.
If the compressor is in a long-term stop without being operated, the pressure in a refrigerating cycle is counterbalanced, and the refrigerant in the refrigerating cycle is liquefied at a portion having the lowest temperature in the refrigerating cycle. As the compressor has the largest thermal capacity among elements that constitute the refrigerating cycle and can hardly be warmed up by following the changes in external temperature, liquefaction of refrigerant in the refrigerating cycle occurs in the compressor. When the refrigerant is liquefied in the compressor, the liquid refrigerant is accumulated in the control pressure chamber.
In the case where the compressor is activated from a state in which the pressure is counterbalanced, the pressure in the inlet chamber is lowered by the operation of the compressor and accordingly, the refrigerant in the control pressure chamber is discharged into the inlet chamber via the bleed passage. However, when the liquid refrigerant is accumulated in the control pressure chamber, the interior of the control pressure chamber is brought into a saturated state in which a gas-phase refrigerant and a liquid-phase refrigerant coexist, and thus the pressure in the control pressure chamber is maintained at a saturation pressure even when the refrigerant in the control pressure chamber is discharged into the inlet chamber via the bleed passage. Therefore, a problem is known in that the pressure in the control pressure chamber is not lowered until the entire liquid refrigerant is vaporized and discharged from the bleed passage, and thus discharge capacity control cannot be performed (the discharge capacity does not increase).
In order to solve the above described problem, a configuration as illustrated in FIG. 8 is known (see PTL1). This configuration includes a first control valve 104 configured to adjust the opening of the supply passage on a supply passage 103 configured to connect a discharge chamber 101 and a control pressure chamber 102, and a second control valve 107 provided on a bleed passage 106 configured to connect the control pressure chamber 102 and an inlet chamber 105, and the second control valve 107 is configured to include a spool housing recess 108 formed on a housing, a spool 109 movably housed in the spool housing recess 108, a back pressure chamber 110 segumentalized in the spool housing recess 108 behind the spool 109, and a biasing spring 112 configured to bias the spool 109 in a direction away from a valve forming body 111, and an intermediate area K between the first control valve 104 of the supply passage 103 and a fixed throttle 113 provided on a downstream side thereof is connected to the back pressure chamber 110 via the branch passage 114.
In this configuration, the first control valve 104 fully closes the supply passage 28, and blocks the communication between the discharge chamber 101 and the control pressure chamber 102 at the time of start-up in which a difference between a pressure Pd of the discharge chamber 101 and a pressure Ps of the inlet chamber 105 is small. Then, a pressure Pk in the intermediate area K in the supply passage 103 on the downstream side of the first control valve 104, that is, the pressure in the back pressure chamber 110 is maintained in substantially the same state as a pressure Pc of the control pressure chamber 102, and thus the spool 109 fully opens the bleed passage 106 by a spring force of the biasing spring 112.
Consequently, even when the liquid refrigerant is accumulated in the control pressure chamber 102, releasing and lowering of the pressure in the control pressure chamber 102 into the inlet chamber 105 via the bleed passage having a large opening degree in the early stage are enabled (time required for the entire liquid refrigerant accumulated in the control pressure chamber 102 to be vaporized and discharged into the inlet chamber 105 is reduced), and hence a problem of increase in time until the discharge capacity control is enabled may be avoided. Therefore, the pressure Pc in the control pressure chamber 102 is lowered by the first control valve 104 fully closed in a rapid manner, and an angle of inclination of the swash plate may increase in a rapid manner to increase the discharge capacity.
Subsequently, when the difference between the pressure Pd in the discharge chamber 101 and the pressure Ps in the inlet chamber 105 gradually increases after the entire liquid refrigerant accumulated in the control pressure chamber 102 is vaporized and discharged to the inlet chamber 105, a fully-closed state of the first control valve 104 is released and the supply passage 103 opens, and the pressure in the intermediate area K (the pressure in the back pressure chamber 110) exceeds the pressure Pc in the control pressure chamber 102. The spool 109 then comes into contact with the valve forming body 111 moving against the biasing spring 112, and the bleed passage 106 is significantly throttled by a communication groove 109a formed at a distal end of the spool 109. Therefore, the amount of the refrigerant introduced from the control pressure chamber 102 to the inlet chamber 105 via the bleed passage 106 significantly decreases, and thus the pressure Pc of the control pressure chamber 102 increases, so that the angle of inclination of the swash plate decreases to decrease the discharge capacity.